Why This Enquiry Mixes Hot Rolled and Cold Rolled Terms
The grade names in this product family, SPCC, SPCD, DC01 and DC02, all belong to cold reduced steel: SPCC and SPCD are JIS G3141 commercial and drawing quality grades, and DC01 and DC02 are the base and second grades of the EN 10130 cold reduced drawing steel family. Hot rolled coil appears in the same enquiry because it is the upstream feedstock. The hot rolled coil is pickled to remove mill scale, cold reduced to final thickness to develop the required properties and surface, then annealed and skin passed. Understanding that sequence explains why the final product carries cold rolled properties even though the order is frequently written alongside hot rolled material.
The distinction is not academic for a buyer. Hot rolled coil is supplied at final thickness with a rougher surface, a wider thickness tolerance and a lower cost per tonne, and it is used for structural parts, pipe feedstock and general fabrication. Cold reduced coil is used where appearance, thickness control and formability decide the outcome. Using the wrong one is a design error that no amount of inspection at receipt can correct.
Grade Cross Reference
| System | Base grade | Drawing grade | Deeper drawing grade |
|---|---|---|---|
| JIS G3141 | SPCC | SPCD | SPCE |
| EN 10130 | DC01 | DC03 | DC04 |
| Common former designation | St12, FeP01 | St13, FeP03 | St14, FeP04 |
| Typical use | Bending, beading, coining | Deep drawing, difficult profiling | High forming requirements |
DC02 is a grade of the same family positioned between the base grade and the drawing grade, and it is no longer part of every current edition of the European standard, which is why a purchase order naming DC02 should always name the standard and edition as well as the grade. Where the requirement is the practical equivalent of DC02, the safe route is to specify the drawing grade with the required mechanical properties stated explicitly, or to order against the standard's current grade list rather than against the older name.
From Hot Rolled Coil to Cold Reduced Coil
The process starts with pickling, normally in hydrochloric acid, which removes the oxide scale from the hot rolled surface and leaves a clean, slightly roughened surface that will accept the cold reduction. Cold reduction then reduces thickness by a large percentage in a tandem mill or a reversing mill, which work hardens the steel severely and produces the required thickness tolerance and surface smoothness. Because the reduction leaves the material hard and unsuitable for forming, the coil is annealed, either in a continuous line or in a batch furnace, to recrystallise the grain structure and restore ductility.
The final step is skin passing or temper rolling, a light reduction of roughly 0.5% to 1.5%. Skin passing flattens the surface, removes the yield point elongation that would otherwise cause stretcher strain during forming, and sets the surface roughness. It also raises the yield strength slightly, so the delivered properties reflect the amount of temper rolling, and a coil temper rolled for surface finish behaves differently in a press from one temper rolled for formability.
Properties and Forming Behaviour
DC01 has a maximum yield strength of 280 MPa, a tensile strength range of 270-410 MPa and an A80 elongation of at least 28% under EN 10130. DC03 lowers the yield ceiling to 240 MPa and raises the elongation to at least 34%, and DC04 goes to 210 MPa and 38%. The pattern is consistent across the standard systems: ductility is bought by lowering the yield strength and the carbon content. For JIS grades, the maximum carbon content falls from SPCC through SPCD to SPCE, which is what allows the deeper draws.
For press work, the parameters that decide whether a part forms cleanly are the tool radius, the blank holder force, the lubricant and the material's forming limit curve. Holding the blank holder force and lubricant constant and changing grade is the normal way to isolate a material problem in a press trial, and it is also the reason a delivered coil that passes the tensile test can still fail in the press if the roughness class is wrong or if the material has aged in storage.
Purchasing, Inspection and Storage
An order for this family should specify the standard and edition, the grade, thickness with a tolerance class, width, surface finish class, roughness class, flatness, edge condition and coil weight range. The delivery certificate should declare the chemical composition, the mechanical properties and the heat number so that results can be traced. Receiving inspection normally covers thickness at several positions across the width, width, flatness, surface condition and the absence of edge damage from handling.
Storage practice decides whether the material can be used at all. Cold reduced steel has no metallic coating, so condensation produces flash rust quickly. Coils should be kept indoors, off the floor, away from open doors and temperature cycling, and processed in rotation. Oil coated material should be used before the oil dries or drains to the bottom of the coil, and any rust discovered at the coil edge should be assessed against the width that will actually be consumed by the blank.
Frequently Asked Questions
Q: Are SPCC and DC01 hot rolled or cold rolled?
A: Both are cold reduced grades. SPCC is defined in JIS G3141 and DC01 in EN 10130, and each describes a cold rolled product. Hot rolled coil is the feedstock that is pickled and cold reduced to make them.
Q: What is the difference between DC01 and DC03?
A: DC01 is intended for simple forming such as bending, embossing and beading, and DC03 for deep drawing and difficult profiling. DC03 has the lower maximum yield strength and the higher minimum elongation of the two.
Q: Should I specify DC02?
A: Confirm the applicable standard and edition first, because the grade list has changed between editions. If the requirement is close to the drawing grade, stating the mechanical properties explicitly against the current standard is the safer approach.
Q: How does hot rolled coil compare on tolerance?
A: Hot rolled coil is produced at final thickness by hot rolling and carries a wider thickness tolerance and a rougher surface than cold reduced coil. Where thickness consistency and surface appearance matter, cold reduced material is the correct choice.
Q: What causes stretcher strain marks on a formed part?
A: Yield point elongation that reappears after the material has aged in storage. Skin passing at the mill suppresses it, so material should be used within a reasonable period after delivery or re-tested if it has been held for a long time.
Q: Does the coil need protection before use?
A: Cold reduced steel has no coating, so it should be kept dry and processed promptly. Parts that will not be painted immediately should be protected with a temporary oil film, and any cut edge left exposed should not be allowed to stand in a humid atmosphere.